In recent years, instead of incandescent light bulbs (filament light bulbs), illuminating devices which employ light emitting diodes (LEDs) as a light source have been adopted for practical applications.
Illuminating devices which use light emitting diodes have a longer lifetime and a lower power consumption, and for this reason, are expected to replace the existing incandescent light bulbs.
However, when light emitting diodes are used as the light source, the light distribution angle is narrower than that of incandescent light bulbs. This is undesirable.
In consideration of this problem, people have proposed an illuminating device having an expanded light distribution angle resulting from the arrangement of multiple light emitting diodes on a curved printed circuit board. However, for such an illuminating device, the ability to dissipate heat generated by the multiple light emitting diodes is poor. This poor heat dissipation limits the electric power that can be applied to the illuminating device for the production of light. Thus, the light output from the light emitting diodes may become less intense and the emission of light from the illuminating device is less than optimal.